Terminal electron transport mechanisms will be studied in selected parasitic protozoa, cestodes and nematodes. Specific electron transport chain components such as cytochromes will be determined in homogenates and in isolated cell organelles, especially mitochondria. The electron flow in final acceptors under both aerobic and anaerobic conditions will be investigated. Major methods employed will be: differential and density gradient centrifugation for separating cell components, low temperature and dual-wavelength spectrophotometry for cytochrome identification, ultraviolet and visible spectrophotometry for enzyme activities, polarography for oxygen utilization, and liquid scintillation counting for quantitation of radioactively-labelled compounds.